Questions like, “Was I really awake for 2 hours 20 minutes straight last night without even noticing? What on earth did I do all that time?"

Or questions like, “Is stirring a roux really more exercise than riding a bicycle uphill? And just what is a roux, anyway?"

Those questions I will address in good time. For now the questions I need to address are these: what on earth is a UP, and how does it work?

As you can probably guess from the picture, the UP is a device you wear on your wrist, preferably a wrist attached to your bad hand. (If you wear it on a wrist attached to your good hand, it doesn’t work so well.)

It’s a bracelet that stretches open in a rubbery fashion so you can get it past your bad hand and onto your wrist. On one end of the bracelet is a button you can use to control the device. On the other end is a headphone jack, which you usually cover with a small plastic cap which you will certainly lose one day. (Don’t fear, Jawbone sells replacement caps.)

But the headphone jack isn’t for audio. Rather, it’s used as a data connector to your Apple or Android smartphone or tablet, on which you run a special UP app that sucks data out of the UP bracelet and presents it to you in a neat graph that’s so fancy and professional looking you could be forgiven for thinking it was accurate.

But is it accurate? That’s one of those questions that is asked, but left unanswered, by the device. The answer is probably yes and no, in roughly equal measure.

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The data the UP gathers is simple: how many steps you’ve taken and at what time, and how long you’ve slept and at what time.

The UP is essentially a very sensitive, very small motion detector that measures your wrist movements and from that extrapolates how many steps you walk in a day and, when you go to bed and put the device into “sleep" mode, extrapolates how long you spent lying awake, how long you were in a state of light sleep, and how long you were in a state of deep sleep.

I’ve spent five days and four nights wearing the UP, and the results have shocked and surprised me. Am I really doing what the UP says I am?

One surprise is how many steps I take when I’m not walking or running. Standing at a stovetop stirring a roux (a mixture of flour and water that goes into a gumbo soup), the UP interpreted as a period of vigorous activity, and calculated I had taken around 800 steps when in fact I had taken only a dozen or so. (Rouxs require constant stirring for long periods.) Sanding and painting garden furniture produced similar results: a lot of steps recorded when few were taken. The way around this, of course, is to wear the UP on your bad hand, which I have been doing for two days now, with much better results.

But even on the bad hand, the UP is far from a perfect measure of my activity. Yesterday, for instance, I was killing myself riding my bicycle up a hill, and the UP buzzed me.

I should mention that the UP has a small buzzer built into it, that you can set to vibrate when, say, you’ve been inactive for 15 minutes, to remind you to stretch your legs.

Having it buzz me every 15 minutes when I’m sitting here writing to you is one thing, but buzzing me when I’m exercising my little heart out, well that’s quite galling, and it shows the limitation of the device: it only measures wrist movements, not pulse rate, not sweat, and it just guesses everything else.

I’m convinced it’s just guessing my sleep, for instance. The UP tells me that most nights, I wake up five times, and I spend around four hours in deep sleep and a couple of hours in light sleep. Maybe so. I’m asleep, so I can only take the UP’s word for it.

But last night, the UP recorded that I was awake from 5.22am to 7.42am. I have no recollection of lying awake for 2 hours 20 minutes, and that’s something I would remember, isn’t it? Is the UP just making stuff up?

The UP may not provide answers, but it does ask a lot of questions, and when it comes to living well, isn’t questioning half the battle?